Reusable injection devices which can be reloaded with a new medicament container when a prior medicament container is emptied are known in prior art. For example, pen injectors for insulin are commonly known. WO-2004/002556 discloses a re-usable pen injector for use with medicament containers, comprising a drive mechanism having a plunger rod acting on a plunger in the container and when the container has been emptied to a pre-defined extent, the plunger rod can be reset to an initial position by unscrewing the two housing parts.